.\"	$OpenBSD: SHA1.3,v 1.7 2018/03/27 17:35:50 schwarze Exp $
.\"	OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org> and
.\" Matt Caswell <matt@openssl.org>.
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.Dd $Mdocdate: March 27 2018 $
.Dt SHA1 3
.Os
.Sh NAME
.Nm SHA1 ,
.Nm SHA1_Init ,
.Nm SHA1_Update ,
.Nm SHA1_Final ,
.Nm SHA224 ,
.Nm SHA224_Init ,
.Nm SHA224_Update ,
.Nm SHA224_Final ,
.Nm SHA256 ,
.Nm SHA256_Init ,
.Nm SHA256_Update ,
.Nm SHA256_Final ,
.Nm SHA384 ,
.Nm SHA384_Init ,
.Nm SHA384_Update ,
.Nm SHA384_Final ,
.Nm SHA512 ,
.Nm SHA512_Init ,
.Nm SHA512_Update ,
.Nm SHA512_Final
.Nd Secure Hash Algorithm
.Sh SYNOPSIS
.In openssl/sha.h
.Ft unsigned char *
.Fo SHA1
.Fa "const unsigned char *d"
.Fa "size_t n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo SHA1_Init
.Fa "SHA_CTX *c"
.Fc
.Ft int
.Fo SHA1_Update
.Fa "SHA_CTX *c"
.Fa "const void *data"
.Fa "size_t len"
.Fc
.Ft int
.Fo SHA1_Final
.Fa "unsigned char *md"
.Fa "SHA_CTX *c"
.Fc
.Ft unsigned char *
.Fo SHA224
.Fa "const unsigned char *d"
.Fa "size_t n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo SHA224_Init
.Fa "SHA256_CTX *c"
.Fc
.Ft int
.Fo SHA224_Update
.Fa "SHA256_CTX *c"
.Fa "const void *data"
.Fa "size_t len"
.Fc
.Ft int
.Fo SHA224_Final
.Fa "unsigned char *md"
.Fa "SHA256_CTX *c"
.Fc
.Ft unsigned char *
.Fo SHA256
.Fa "const unsigned char *d"
.Fa "size_t n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo SHA256_Init
.Fa "SHA256_CTX *c"
.Fc
.Ft int
.Fo SHA256_Update
.Fa "SHA256_CTX *c"
.Fa "const void *data"
.Fa "size_t len"
.Fc
.Ft int
.Fo SHA256_Final
.Fa "unsigned char *md"
.Fa "SHA256_CTX *c"
.Fc
.Ft unsigned char *
.Fo SHA384
.Fa "const unsigned char *d"
.Fa "size_t n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo SHA384_Init
.Fa "SHA512_CTX *c"
.Fc
.Ft int
.Fo SHA384_Update
.Fa "SHA512_CTX *c"
.Fa "const void *data"
.Fa "size_t len"
.Fc
.Ft int
.Fo SHA384_Final
.Fa "unsigned char *md"
.Fa "SHA512_CTX *c"
.Fc
.Ft unsigned char *
.Fo SHA512
.Fa "const unsigned char *d"
.Fa "size_t n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo SHA512_Init
.Fa "SHA512_CTX *c"
.Fc
.Ft int
.Fo SHA512_Update
.Fa "SHA512_CTX *c"
.Fa "const void *data"
.Fa "size_t len"
.Fc
.Ft int
.Fo SHA512_Final
.Fa "unsigned char *md"
.Fa "SHA512_CTX *c"
.Fc
.Sh DESCRIPTION
SHA-1 (Secure Hash Algorithm) is a cryptographic hash function with a
160-bit output.
.Pp
.Fn SHA1
computes the SHA-1 message digest of the
.Fa n
bytes at
.Fa d
and places it in
.Fa md ,
which must have space for
.Dv SHA_DIGEST_LENGTH
== 20 bytes of output.
If
.Fa md
is
.Dv NULL ,
the digest is placed in a static array, which is not thread safe.
.Pp
The following functions may be used if the message is not completely
stored in memory:
.Pp
.Fn SHA1_Init
initializes a
.Vt SHA_CTX
structure.
.Pp
.Fn SHA1_Update
can be called repeatedly with chunks of the message to be hashed
.Pq Fa len No bytes at Fa data .
.Pp
.Fn SHA1_Final
places the message digest in
.Fa md ,
which must have space for
.Dv SHA_DIGEST_LENGTH
== 20 bytes of output, and erases the
.Vt SHA_CTX .
.Pp
The SHA224, SHA256, SHA384, and SHA512 families of functions operate
in the same way as the SHA1 functions.
Note that SHA224 and SHA256 use a
.Vt SHA256_CTX
object instead of
.Vt SHA_CTX ,
and SHA384 and SHA512 use
.Vt SHA512_CTX .
The buffer
.Fa md
must have space for the output from the SHA variant being used:
.Dv SHA224_DIGEST_LENGTH ,
.Dv SHA256_DIGEST_LENGTH ,
.Dv SHA384_DIGEST_LENGTH ,
or
.Dv SHA512_DIGEST_LENGTH
bytes.
.Pp
Applications should use the higher level functions
.Xr EVP_DigestInit 3
etc.  instead of calling the hash functions directly.
.Pp
The predecessor of SHA-1, SHA, is also implemented, but it should be
used only when backward compatibility is required.
.Sh RETURN VALUES
.Fn SHA1 ,
.Fn SHA224 ,
.Fn SHA256 ,
.Fn SHA384 ,
and
.Fn SHA512
return a pointer to the hash value.
The other functions return 1 for success or 0 otherwise.
.Sh SEE ALSO
.Xr EVP_DigestInit 3 ,
.Xr HMAC 3 ,
.Xr RIPEMD160 3
.Sh STANDARDS
SHA: US Federal Information Processing Standard FIPS PUB 180 (Secure
Hash Standard), SHA-1: US Federal Information Processing Standard FIPS
PUB 180-1 (Secure Hash Standard), ANSI X9.30
.Sh HISTORY
.Fn SHA1 ,
.Fn SHA1_Init ,
.Fn SHA1_Update ,
and
.Fn SHA1_Final
first appeared in SSLeay 0.5.1 and have been available since
.Ox 2.4 .
.Pp
The other functions first appeared in OpenSSL 0.9.8
and have been available since
.Ox 4.5 .
